In various sliding guide apparatuses containing bearing, by using rolling motion of rolling elements such as balls or rollers interposed between a track rail and a moving body, relative linear motion or rotary motion between the track rail and moving body is enabled. To (1) prevent the rolling elements from falling out of the moving body when the moving body is separated from the track rail, (2) reduce frictional resistance by avoiding relative contact between respective rolling elements, and (3) arrange the rolling elements at predetermined positions so as to secure a smooth motion or the like, generally a plurality of the rolling elements are incorporated between the track rail and moving body while being held by rolling element retainer or rolling element cage made of metallic thin plate or synthetic resin.
However, in a sliding guide apparatus using a conventional rolling element retainer, this rolling element retainer is incorporated in the moving body and then the rolling elements are incorporated in a rolling path formed for the rolling elements. Then, the moving body is installed on the track rail. Particularly if this sliding guide apparatus contains a full track of the rolling elements, assembly work for this sliding guide apparatus using the rolling element retainer requires experienced skill, so that automation thereof is difficult.
In the sliding guide apparatus using the conventional rolling element cage, the rolling element cage has a plurality of pockets such that respective rolling elements are rotatably held in these pockets. Thus, assembly work for incorporating the plurality of the rolling elements into the sliding guide apparatus is easy. However, because it is necessary to incorporate the plurality of the rolling elements in the respective pockets of the rolling element cage and hold them so that they do not slip out, it takes time and labor to produce this rolling element cage itself.
Therefore, to solve such problem, various ball chains which are produced by injection molding of resin with balls being disposed as inner ring on a substantially flat plane in a mold so that they are incorporated without an end in a full track of a moving body have been proposed (Japanese Examined Patent Publication No. Hei 6-56181, Japanese Unexamined Patent Application No. Hei 5-52217, Japanese Unexamined Patent Application No. Hei 5-126149, Japanese Unexamined Patent Application No. Hei 5-196036, Japanese Unexamined Patent Application No. Hei 5-196037).
In this conventional ball chain, after the ball chain is incorporated in a full track of a moving body, both end portions thereof are connected to each other so as to form an endless ball chain. However, this connecting work is very troublesome.
In such a sliding guide apparatus, following so-called ball selective engagement method has been applied to support four directional loads including radial, reverse radial and right/left direction loads between the moving body and track rail, and further improve accuracy of reciprocation of the moving body relative to the track rail and stiffness thereof. That is, pre-pressure is applied to each ball of the ball chain interposed between the moving body and track rail or this pre-pressure may be sometimes adjusted. To apply the pre-pressure and adjust it, as a general easy method, a ball having a slightly larger size than a dimension of a gap between the loaded rolling path of the moving body and a rolling path of the track rail is selected and engaged. At this time, its sliding resistance and stiffness are measured so as to determine the size of a ball for use.
However, in the sliding guide apparatus using the aforementioned conventional ball chain, when this ball selective engagement is carried out, if the ball chain first incorporated in the moving body and connected endlessly has not achieved a desired sliding resistance and stiffness due to its ball diameter, this endless connection of the ball chain must be released so as to create ends thereof and that ball chain having the ends must be removed from the moving body. Then, another ball chain having ends and a different ball diameter is incorporated in the moving body and connected endlessly. Whether or not this incorporated ball chain has achieved its desired sliding resistance and stiffness is investigated. Until the ball diameter of the ball chain incorporated in the moving body achieved its desired sliding resistance and stiffness, the same procedure must be repeated. As a result, the ball selective engagement method which is essentially a simple method for application of pre-pressure and adjustment thereof, conversely becomes a very complicated method.